2 tablespoons extra-virgin olive oil
2 large onions, halved and thinly sliced
1 tablespoon sugar
2 cinnamon sticks
Pinch red pepper flakes
Kosher salt and freshly ground black pepper
1/4 cup red wine vinegar
1/4 cup chopped fresh mint
1/4 cup chopped fresh parsley, plus whole leaves for garnish
4 tuna steaks, 1 1/2-inches thick
2 tablespoon canola oil